1. Field of the Invention
The present invention relates to a recording tape cartridge rotatably accommodating a single reel on which a recording tape is wound.
2. Description of the Related Art
Conventionally, among recording tape cartridges used as recording media used in external storage devices of computers for example, a type is known in which a single reel is rotatably accommodated in the recording tape cartridge. A recording tape, such as a magnetic tape, is wound on the reel within the recording tape cartridge.
The magnetic tape is used for, for example, storage of data of a computer, and there are cases in which important information is recorded thereon. In this case, the recording tape cartridge is structured such that the magnetic tape cannot be inadvertently pulled-out therefrom at the time when the recording tape cartridge is not in use (e.g., when the recording tape cartridge is being stored), so that trouble such as jamming of the tape or the like does not occur.
The reel is structured by a reel hub and upper and lower flanges which are provided at the both end portions of the reel hub. As shown in FIGS. 8 and 9, a reel hub 100 and a lower flange 102 are molded integrally. After molding, an upper flange 104 is welded so that a reel 106 is formed.
The reel hub 100 has a driven gear 108 which meshes with a driving gear 105 which transmits driving force from a driving device 103 of a drive device. An annular metal plate 110 for magnetic attraction is provided at the inner side of the driven gear 108. Due to the metal plate 110 being attracted to a magnet (not shown) provided at the driving device 103 of the drive device, axial offset is prevented, and the state in which the driven gear 108 and the driving gear 105 are meshed together is maintained.
Moreover, a lock gear 112 is formed at an inner surface of the reel hub 100 which is positioned at the opposite side of the driven gear 108. The lock gear 112 meshes with a braking gear 114A provided at a braking member 114, so as to prevent rotation of the reel 106.
A lock releasing portion 107 provided at the driving device 103 of the drive device can be inserted through a hole 110A formed in the metal plate 110. The braking member 114 is pushed up by the lock releasing portion 107, the meshed state of the braking gear 114A and the lock gear 112 is cancelled, and the reel 106 becomes able to rotate.
Three through holes 116 are formed at equal intervals in the metal plate 110. As shown in FIG. 10A, a reduced diameter portion 116A is formed at the inner peripheral edge portion of the through hole 116. A boss 118, which is of a size such that it can be inserted through the reduced diameter portion 116A, stands erect at the reel hub 100 at the position where the metal plate 110 is mounted.
After the reel hub 100 and the lower flange 102 (see FIG. 9) are molded, as shown in FIG. 10B, the bosses 118 are inserted through the reduced diameter portions 116A. As shown in FIG. 10C, the distal end portions of the bosses 118 are caulked, such that the metal plate 110 is prevented from coming off of the reel hub 100.
In this way, the metal plate 110 and the reel hub 100 are made integral. However, after the reel hub 100 and the lower flange 102 are molded, the metal plate 110 is made integral with the reel hub 100 by outsert molding. Thus, the number of work processes increases, which leads to an increase in manufacturing costs.
Thus, it has been thought to make the metal plate 110 integral with the reel hub 100 by insert molding. However, in order to reduce the dispersion of the reel hub 100 caused by molding, it is better to set the gate positions as near as possible to the axial center side.
The annular metal plate 110 is disposed at the axial center side of the reel hub 110. Thus, there is a method in which the molding material is filled in from the inner surface side of the reel hub 100 so as to flow over the hole 110A of the metal plate 110 by submarine gates. In cases in which the hole 110A of the metal plate 110 is small, it is difficult to provide a plurality of submarine gates.